Oceania vs Oceanica

Oceania and Oceanica both are nouns.

Word	Noun	Adjective	Verb	Adverb
Oceania	Yes	No	No	No
Oceanica	Yes	No	No	No

As nouns, Oceania and Oceanica are synonyms defined as:

Oceania and Oceanica: a large group of islands in the south Pacific including Melanesia and Micronesia and Polynesia (and sometimes Australasia and the Malay Archipelago)

Oceania (noun)	Oceanica (noun)
a large group of islands in the south Pacific including Melanesia and Micronesia and Polynesia (and sometimes Australasia and the Malay Archipelago)	a large group of islands in the south Pacific including Melanesia and Micronesia and Polynesia (and sometimes Australasia and the Malay Archipelago)